The main thrust of this project is to characterize the immunological mechanisms in the Syrian hamster and mink, particularly the role played by various Ig classes. Experiments are devised to determine why only one Ig class may be preferentially stimulated depending upon antigenic presentation, what are the relative protective roles (phagocytosis promoting, tumor suppression or enhancement, etc.) of each Ig class and how can the immune response be channeled for synthesis in one or another Ig class. BIBLIOGRAPHIC REFERENCES: Coe, J. E.: A sex-limited serum protein of Syrian hamsters: definition of female protein and regulation by testosterone. Proc. Natl. Acad. Sci. 74: 730-733, 1977. Saxon, A. and Portis, J.: Lymphoid subpopulation changes in regional lymph nodes in squamous head and neck cancer. Cancer Res. 37: 1154-1158, 1977.